The trendy sparkling water brand LaCroix claims it is all natural, but a new class-action lawsuit says the “water is neither all natural or 100% natural” and seeks to “obtain redress for all persons injured” by the claim.

“LaCroix contains, among other things: ethyl butanoate, limonene, linalooland linalool propionate,” the complaint states. “The above chemical compounds are synthetically created and added to consumable goods to make those goods taste or smell a certain way.” Perhaps most disturbingly, it describes linalool as an ingredient in cockroach insecticide.

Despite the lawsuit’s scary implications, it’s not alleging that LaCroix sodas are causing people harm. Instead, it hinges on the question of whether these particular ingredients are synthetic or natural.

Those four chemicals can be synthetic or come from natural sources. Here’s a bit more information about each one:

Ethyl butanoate is a chemical that is used to simulate the flavor of pineapple and can come from natural sources or be synthesized.

Limonene is a “major component of the oil extracted from citrus peels.”

Linalool is produced by many flowers and spice plants, including mint, herbs, and citrus fruits, and has a floral, spicy scent.

LaCroix’s ingredients labels all say, simply, “Carbonated water, natural flavor.” If these compounds indeed are in LaCroix, the question becomes whether they are the natural or synthetic form.

The agency that oversees such claims about food, the US Food and Drug Administration, says it considers the term “natural” “to mean that nothing artificial or synthetic (including all color additives regardless of source) has been included in, or has been added to, a food that would not normally be expected to be in that food.”

The law firm that filed the lawsuit, Beaumont Costales, declined to provide information to BuzzFeed News about how it tested for these chemicals and how it knows they are synthetic.

BuzzFeed News asked the American Chemistry Council whether these are natural flavors, but the group referred us back to the manufacturer.

The maker of LaCroix, National Beverage, fully denied the allegations in a statement, saying, “Natural flavors in LaCroix are derived from the natural essence oils from the named fruit used in each of the flavors. There are no sugars or artificial ingredients contained in, nor added to, those extracted flavors. All essences contained in LaCroix are certified by our suppliers to be 100% natural.”

National Beverage said the claims were made “without basis in fact or law regarding the natural composition of its LaCroix sparkling waters.” The company did not immediately respond to an inquiry from BuzzFeed News.

Whether a food is legitimately “natural” has been the subject of a number of lawsuits. Most recently, General Mills dropped the “100% natural” label from Nature Valley bars to settle a lawsuit claiming the use of an herbicide in the oats meant the product could not make such a claim. Monster Beverage also settled a lawsuit this summer over natural claims made on its Hansen’s juices and Hubert’s lemonade.

UPDATE

Oct. 05, 2018, at 20:24 PM

The sources for this story have been updated.

Venessa Wong is a deputy business editor for BuzzFeed News and is based in New York.